1. Field of the Invention
This invention relates to a quick-release type clamping assembly for releasably or removably mounting a wheel hub to a pair of fork ends of a bicycle frame. It relates more particularly to such a clamping assembly which is improved to prevent unexpected removal or detachment, from the fork ends, of the hub in its mounted condition.
2. Description of the Prior Art
In bicycles, generally, it is often required to remove a wheel hub from a pair of fork ends of a bicycle frame for replacement or repair for example. For this purpose, Japanese Utility Model Application Laid-open No. 57-12301 (Laid-open: Jan. 22, 1982; Application No.: 55-90471; Filed: June 26, 1980; Applicant: Shimano Industrial Company Limited; Inventor: Keizo SHIMANO) discloses a quick-release type clamping assembly for a bicycle hub which enables quick removal of the hub when required.
More particularly, the clamping assembly of the above laid-open utility model application comprises a tie rod extending through a tubular hub shaft on which is rotatably supported a hub shell between a pair of fork ends. The tie rod has one end screwed to an end nut positioned axially outwardly from one fork end. The other end of the rod is provided with an enlarged head positioned axially outwardly from the other fork end and having a cam hole extending transversely of the rod. A hollow presser member is fitted around the enlarged head and axially movable relative thereto toward and away from the end nut. A lever, which is pivotable about a pivotal axis between a clamping position and a releasing position, is mounted to the presser member and has a cam portion received within the cam hole and eccentric relative to the pivotal axis.
When the lever is pivoted to the clamping position, the presser member is moved axially inwardly toward the end nut due to the eccentricity of the cam portion. As a result, the distance between the end nut and the presser member is reduced to clamp the hub (hub shaft and hub shell) to the fork ends.
Conversely, when the lever is pivoted to the releasing position, the presser member is moved axially outwardly away from the end nut, so that the hub and the fork ends are relieved from the previous clamping force to enable removal of the hub (wheel).
As described above, the quick-release type clamping assembly has an advantage of enabling quick mounting and removal of the hub. However, in such a clamping assembly, it is necessary to properly adjust the clamping force by previously selecting the initial axial position of the end nut on the tie rod. If this initial adjustment is improper, the clamping force may be insufficient for firmly clamping the hub to the fork ends. Therefore, the hub or the wheel may unexpectedly come off the fork ends during riding. This disadvantage becomes particularly pronounced when running on rough roads.
In order to overcome such a disadvantage, Japanese Utility Model Application Laid-open No. 62-127004 (Laid-open: Aug. 12, 1987; Application No.: 61-15477; Filed: Feb. 5, 1986; Applicant: Sansin Engineering, Inc.; Inventor: Mamoru KAWAI) proposes a quick-release type clamping assembly, which in addition to the elements already described above, comprises a stopper washer interposed between the presser member and a corresponding fork end. Such a washer may be alternatively or additionally interposed between the end nut and the other fork end. The stopper washer has an engaging projection for engagement, from above, with the fork end to prevent the hub from moving downward relative to the fork end.
The provision of the stopper washer serves to prevent the hub from being unexpectedly removed from the fork ends during riding. However, since the washer is arranged in a very small space between the presser member and the corresponding fork end (and/or between the end nut and the other fork end), it is difficult, in a hub mounting operation, to angularly adjust the washer so that it engages a suitable portion of the fork end, thereby detracting much from the quick operability of the clamping assembly. Further, the washer is freely movable on the tie rod and therefore may be easily lost when the end nut is screwed out of the tie rod for removal of the clamping assembly from the hub.